What this duty estimate assumes
This estimate applies each state’s general owner-occupier rate to the figure entered, and it excludes everything that moves the real assessment. It excludes first home buyer exemptions and concessions, the principal place of residence concession, off-the-plan concessions, and any foreign purchaser surcharge. Revenue NSW notes that foreign persons acquiring residential-related property “may need to pay surcharge purchaser duty”.
It also assumes the number entered is the number that will be taxed, and that is the assumption most likely to be wrong. Duty is charged on the dutiable value, which Revenue NSW defines as “the higher of: the purchase price you agreed to pay, or the property’s market value”.
A worked example. A property with a market value of 900,000 dollars is sold to a family member for 700,000 dollars. Illustrative figures, not a transaction. A calculator fed 700,000 returns the duty on 700,000; the assessment will issue on 900,000, because that is the higher of the two. The difference between those two duty amounts is not a discount that was missed. It is a number that was never available.
The conclusion to draw is to enter the market value wherever it differs from the contract price, and to expect the revenue office to require evidence of value where the two are far apart. A gift with no money changing hands is still a dutiable transaction. One further reason an estimate is dated: in New South Wales the thresholds and rates for general transfer duty and premium duty “are adjusted each year in line with Consumer Price Index (CPI) changes”, so a figure worked out this financial year is not necessarily the figure that applies to the same price next year. Only the revenue office for the state the property is in can issue an assessment.
Longer read: Why the same purchase costs different duty in every state. Transfer duty is eight separate taxes wearing one name. They differ on what is taxed, on how the brackets move, and on concessions that end at a threshold rather than tapering away to nothing.
Why an identical purchase costs different duty in each state, and where the first home concession ends, is covered in why the same purchase costs different duty in every state. The mortgage repayment calculator covers the monthly commitment that begins around the same date.